1. Field of the Invention
The present invention relates to an airbag for use in a motor vehicle. More particularly, the present invention relates to a front or side airbag having passive internal pressure regulation.
2. Description of Related Art
Airbags which do not have any mechanisms for situation-dependent regulation of the internal pressure are only ideal for a vehicle occupant of a certain weight and height in certain specific accident situations. For different size occupants accidents in different accident situations from those specified, the airbag is either too hard or too soft. If, for example, such an unregulated airbag is designed for a male wearing a seat belt who is 1.80 m tall and who weighs 80 kg, such an airbag will be too hard for a female wearing a seat belt who is 1.65 m tall and weighs 60 kg and too soft for the male described above not wearing a seat belt.
In order to counteract this problem, airbags are known with at least one passive venting arrangement via which the gas can exit from the airbag and regulate the pressure. The gas stream can be throttled by this venting arrangement depending on the situation. In addition, active systems exist where, for example, sensors measure the weight of the occupants and electrically adjust the effective cross-section of the venting arrangement based on the sensor measurements. However, such systems are complex and expensive and susceptible to operational errors.
An airbag with variable internal pressure is known from U.S. Pat. No. 6,419,267 whose internal pressure depends on the size of the vehicle occupant to be retained, and includes a passive venting arrangement. This airbag includes an inner and outer airbag cover. The inner cover includes holes or permeable fabric in a certain area, so that gas can penetrate from the gas chamber which is surrounded by the inner airbag cover into the area between the inner airbag cover and the outer airbag cover and from there can fully exit from the airbag. If a vehicle occupant strikes against the outer airbag cover, this cover is pressed in sections onto the inner airbag cover, so that a part of the holes or the permeable fabric is covered and the gas stream is reduced. The larger the occupant who strikes the airbag, the more the airstream is throttled and therefore the harder the airbag.
Because of this cover design, the airbag becomes relatively heavy and requires a relatively large volume of space when folded. Furthermore, such an airbag becomes strongly cushion-shaped during filling, so that it is difficult to implement a side airbag with this design.
In view of the above, it is apparent that there exists a need for an improved airbag capable of regulating its internal pressure that is smaller, lighter, and can be configured as a side airbag.